1. Whisk together cornstarch and 2 tablespoons milk.
2. Bring water to a boil in a 2-quart heavy saucepan, then reduce heat to moderately low and add chopped chocolate and a pinch of salt, whisking until smooth.
3. Add cream and remaining milk (1 1/4 cups plus 2 tablespoons) and increase heat to moderate, then cook, whisking occasionally, until mixture is smooth and heated through. Taste; for a deeper chocolate flavor, whisk in cocoa.
4. Whisk cornstarch mixture, then add half to chocolate mixture and simmer, whisking, until slightly thickened, about 2 minutes. Add brandy (if using) and remaining cornstarch mixture to thicken if desired, then simmer, whisking, 1 minute.

Yield: 8 servings